1. Field of the Invention
The present invention relates to the optical record playback equipment which equipped optical recording media, such as an optical disc, with the optical head which performs record or playback of data, and this optical head.
2. Description of the Related Art
An optical head irradiates an optical disc used as the predetermined diameter of spot. An objective lens receives the reflective light. Moreover, it becomes an objective lens drive which drives an objective lens in the direction of tracking, and the direction of a focus from two or more optical elements. The optical system, and an objective lens drive unit and an optical system are carried, and housings in which a slide is possible are consisted of by the radial direction of the optical disc.
Among the components of an optical head explained above, housing is formed with various metal, such as zinc (Zn), aluminum (aluminum), and magnesium (Mg), or these alloys, in order to secure desired rigidity (for example, refer to Japanese Patent No. 2005-285166).
Hereafter, this art is called the 1st conventional example.
It is necessary to carry out straight line movement in a parallel field to the data recording side of an optical disc radially, always maintaining correctly the distance of the data recording side of an optical disc, and an objective lens, when carrying out the slide of the optical head of the above-mentioned composition. Therefore, two main-bearings which have a circle-shaped section mostly set a prescribed interval in the one side surface of housing, and are provided in it. In this housing, the sub-bearing which has an about U character-shaped section is provided in the side of the opposite side which sandwiched the objective lens. And a cylinder-shaped main-shaft is inserted in a main-bearing, and a cylinder-shaped sub-shaft is inserted in a sub-bearing.
A common material of the above-mentioned main-shaft and sub-shaft is stainless steel, and, generally the Vickers hardness is 200 (equivalent to 4 of Mohs hardness) grades. On the other hand, zincky (Zn) Mohs hardness is 2.5, the Mohs hardness of aluminum (aluminum) is 2.9, the Mohs hardness of magnesium (Mg) is 2.0 and all are lower than stainless hardness.
Therefore, in an optical disc, when seek operation is repeated also millions times, the sub-bearing of housing may be worn out depending on the shape of the bearing of housing, the physical relationship of an axis, and accuracy of dimension. If a sub-bearing was worn out, in order that the whole optical head might incline, it did not converge correctly the light beam emitted from an objective lens on the data logging side of the optical disc, but there was a possibility that it might become impossible to perform record or playback of data to an optical disc.
So, while constituting housing and a sub-bearing on another object, there are some which allocated another member formed in the sliding portion with the sub-shaft of a sub-bearing with the resin material in the conventional optical head (for example, refer to Japanese Patent No. 2004-348794.).
Hereafter, this art is called the 2nd conventional example.
In the optical head which has the sub-bearing formed united with housing which consists of metal like the 1st above-mentioned conventional example whose hardness is lower than the metal which constitutes a sub-shaft, after wearing the sub-bearing out, the optical disc had a possibility that it might become impossible to perform record or playback of data.
While constituting housing and a sub-bearing on another object like the 2nd above-mentioned conventional example, when another member is allocated in a sliding portion with the sub-shaft of a sub-bearing, the number of parts increases. The process of attaching another member to a sub-bearing, and the process of attaching a sub-bearing to housing are required, and an optical head becomes expensive.
There is a possibility that the sub-bearing itself may separate from housing at the time of operation of an optical head.
Moreover, when it miniaturizes optical record playback equipment, there are various restrictions on a size, but this restriction cannot be filled with composition like the 2nd above-mentioned conventional example.
Therefore, the miniaturization of optical record playback equipment is unrealizable.
Therefore, in the optical head which has housing which consists of metal whose hardness is lower than the metal which constitutes a sub-shaft, it is requested that wear of a sub-bearing is lessened as much as possible, without providing the sub-bearing of housing and another object.